HP LaserJet Enterprise 600 Printer M603 series - Manual (Page 195)

Clear jams from the optional 5-bin mailbox
1. Remove any paper that is in the output bins.
2. On the back of the 5-bin mailbox, open the
jam-access door.
3. If the paper is jammed at the top of the 5-bin
mailbox, pull it straight down to remove it.
ENWW Clear jams 179